1. Field of the Invention
This invention relates to the application and curing of organosiloxane coating compositions. More particularly, this invention relates to a method and an apparatus for applying coatings of molten, moisture curable organosiloxane compositions that cure in a controlled and reproducible manner.
2. Background Information
It is known to liquify adhesives and coating composition that are solids under ambient conditions by heating the materials above their melting point and applying the resultant liquid to a substrate by spraying, dipping or other conventional coating methods. The molten materials are often referred to in the prior art as "hot melt" compositions.
The use of a heated air stream generated by a blower to both melt an adhesive and heat the surfaces to be bonded is described in U.S. Pat. No. 4,642,158, which issued on Feb. 10, 1987.
The addition of materials containing adsorbed or chemically combined water to moisture curable hot melt adhesives or sealants containing isocyanate groups is described in British patent no. 2,137,638.
The use of gas currents to control the contour and/or direction of a stream of molten coating material as it travels from its source to the substrate is known. For example, European Patent Application No. 363,799 teaches using compressed air at ambient temperature to form an atomized spray of a hot melt adhesive that is guided toward the substrate by air jets directed obliquely downward on to the atomized mixture.
A method for preparing non-curable organosiloxane hot melt pressure sensitive adhesives is described in U.S. Pat. No. 4,865,920, which issued to Randall Sweet.
Moisture curable hot-melt organosiloxane compositions are described in commonly owned copending applications filed in the United States Patent and Trademark Office. It has heretofore not been feasible to apply these compositions as uniform coatings that cure in a reproducible manner irrespective of the temperature and humidity in the area of the coated substrate. One objective of the present invention is to provide such a method.